For almost the last 50 years, we Americans have lived according to the "freeway exit" rule: We've driven out as far as necessary until we reach a point where the houses are affordable. This worked well to bring people into the middle class lifestyle for nearly 3 generations.

But right now, Clark believes we are at a time when we're turning back inward. People don't want the long commute or to have to deal with a yard on the weekends. There's a boomerang effect among baby boomers that are now empty nesters. Meanwhile, people who came of age in the last 10 years are becoming "new urbanists."

These new urbanists have a car but feel disconnected from the suburbs and crave the interaction of a city. Of course, today's high gas prices provide a direct economic incentive for new urbanism.

If Clark is right about people turning back inward, that means price appreciation will dwindle in the distant suburbs. In-town neighborhoods will have the greatest increase in value, followed by close-in neighborhoods. In some extreme cases, suburban homes may not even keep up with the inflation rate.

There are also some serious implications for public transportation here. In short, cities like Dallas, Houston, Atlanta and Charlotte have growth corridors that could support more of it. This is separate from the issue of energy.

The price of gas will not necessarily trend upward forever like the headlines proclaim. But even if energy prices decline, Clark still thinks that in the long run you may want to look closer in if you're thinking of real estate as an investment.